Minify AMP CSS in <style> with PHP/Laravel

minify-amp.php

In blade:
<style amp-custom>
    {!! \App\Helpers\Minify::amp_custom() !!}
</style>





Create a file Minify.php

<?php

namespace App\Helpers;
use View;

class Minify
{
    public static function amp_custom()
    {
        return self::minify_css(View::getSection('amp-custom'));
    }

    public static function minify_css($input)
    {
        if(trim($input) === "") return $input;
        return preg_replace(
            array(
                // Remove comment(s)
                '#("(?:[^"\\\]++|\\\.)*+"|\'(?:[^\'\\\\]++|\\\.)*+\')|\/\*(?!\!)(?>.*?\*\/)|^\s*|\s*$#s',
                // Remove unused white-space(s)
                '#("(?:[^"\\\]++|\\\.)*+"|\'(?:[^\'\\\\]++|\\\.)*+\'|\/\*(?>.*?\*\/))|\s*+;\s*+(})\s*+|\s*+([*$~^|]?+=|[{};,>~]|\s(?![0-9\.])|!important\b)\s*+|([[(:])\s++|\s++([])])|\s++(:)\s*+(?!(?>[^{}"\']++|"(?:[^"\\\]++|\\\.)*+"|\'(?:[^\'\\\\]++|\\\.)*+\')*+{)|^\s++|\s++\z|(\s)\s+#si',
                // Replace `0(cm|em|ex|in|mm|pc|pt|px|vh|vw|%)` with `0`
                '#(?<=[\s:])(0)(cm|em|ex|in|mm|pc|pt|px|vh|vw|%)#si',
                // Replace `:0 0 0 0` with `:0`
                '#:(0\s+0|0\s+0\s+0\s+0)(?=[;\}]|\!important)#i',
                // Replace `background-position:0` with `background-position:0 0`
                '#(background-position):0(?=[;\}])#si',
                // Replace `0.6` with `.6`, but only when preceded by `:`, `,`, `-` or a white-space
                '#(?<=[\s:,\-])0+\.(\d+)#s',
                // Minify string value
                '#(\/\*(?>.*?\*\/))|(?<!content\:)([\'"])([a-z_][a-z0-9\-_]*?)\2(?=[\s\{\}\];,])#si',
                '#(\/\*(?>.*?\*\/))|(\burl\()([\'"])([^\s]+?)\3(\))#si',
                // Minify HEX color code
                '#(?<=[\s:,\-]\#)([a-f0-6]+)\1([a-f0-6]+)\2([a-f0-6]+)\3#i',
                // Replace `(border|outline):none` with `(border|outline):0`
                '#(?<=[\{;])(border|outline):none(?=[;\}\!])#',
                // Remove empty selector(s)
                '#(\/\*(?>.*?\*\/))|(^|[\{\}])(?:[^\s\{\}]+)\{\}#s'
            ),
            array(
                '$1',
                '$1$2$3$4$5$6$7',
                '$1',
                ':0',
                '$1:0 0',
                '.$1',
                '$1$3',
                '$1$2$4$5',
                '$1$2$3',
                '$1:0',
                '$1$2'
            ),
        $input);
    }

}